Oxygen gas transfer through oak barrels: a macroscopic approach

The oak barrel maturation step is nowadays strongly rooted in the production of quality wines. Two main physico‑chemical phenomena contribute to the modification and improvement of wine: the solubilisation of volatile and non-volatile wood compounds concomitant with the dissolution of oxygen from the air into the wine. Indeed, wood is a porous material and gas transfer (especially oxygen transfer, expressed as oxygen transfer rate or OTR) through oak barrels, is an intrinsic parameter which ensures wine oxygen supply during maturation. Due to its oenological impact, it has been actively studied over recent decades using several approaches based on the same principle: the monitoring of oxygen in a model wine solution in the barrel. This project aimed at assaying barrel OTR by using a new tool based on the theoretical knowledge of gas transfer through porous materials. An oxygen concentration gradient was created on each side of a barrel kept in an airtight stainless-steel tank. The concentration of the oxygen in the atmosphere around the barrel was monitored in order to quantify oxygen transfer, thus the avoiding common drawbacks of interactions between dissolved oxygen ingress kinetics and the consumption of oxygen in the liquid phase by wood components. This study reports for the first time, the diffusion coefficient of entire oak barrels (Q. sessilis) to be between 10-10 and 10-9 m²/s, and it contributes to increasing knowledge on the complex phenomena driving oxygen ingress during the maturation of wine in barrels kept in cellar conditions. The results highlight the important role of wood moisture content in oxygen transfer, and provides a simple and reliable parameter to monitor it: the weight of the barrel. Following methodology developed by the authors, the OTR of a new oak barrel was found to be 11.4 mg/L per year. Taking into account the oxygen released through the wood pores, a new barrel will contribute 14.4 mg/L per year of oxygen to the wine, of which 46 % in the first three months of aging.

Failure Investigation of a Corrosion Leak in a C77 Block and Tubing Bonnet in a Chemical Injection System – A Case History

This paper presents a case history outlining the investigation performed to evaluate the causes of failure between a C77 block and tubing bonnet line, used for delivering scale inhibitor to a production well. The data review indicated that the failure occurred as a result of synergistic corrosion effects, including incompatibility between the scale inhibitor chemical and the metallurgies of the block (13Cr SS) and tubing (carbon steel). The analysis showed that while each of the relevant corrosion mechanisms (oxygen corrosion, galvanic and localised corrosion) may not be the root cause for the failure individually, in combination they proved detrimental to system integrity. The study also highlighted that while chemical inhibitor compatibility testing with appropriate flow-wetted metallurgies is common practice, the environment and configuration used for testing is not always representative of the field conditions or specific process operations (e.g., oxygen ingress due to unblanketed tanks, presence of dissimilar materials). In the present case, for example, the most significant oxygen sources were found to be the dissolved oxygen in the tap water used to mix the scale inhibitor to make up the final formulation; and the glycol blended into the product to give it ‘winterised’ properties. Lastly, the paper summarises the recommendations that were put forth to address the issue, such as evaluation of different metallurgies, a more suitable scale inhibitor and implementation of process monitoring, especially of oxygen levels.

Oxygen Induced Phase Transformation in TC21 Alloy with a Lamellar Microstructure

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix.

Quantifying the effect of oxygen on micro-mechanical properties of a near-alpha titanium alloy

Titanium alloys are widely used in the aerospace industry, yet oxygen ingress can severely degrade the mechanical properties of titanium alloy components. Atom probe tomography (APT), electron probe microanalysis (EPMA) and nanoindentation were used to characterise the oxygen-rich layer on an in-service jet engine compressor disc, manufactured from the titanium alloy TIMETAL 834. Oxygen ingress was quantified and related to changes in mechanical properties through nanoindentation studies. The relationship between oxygen concentration, microstructure, crystal orientation and hardness has been explored through correlative hardness mapping, EPMA and electron backscatter diffraction (EBSD). It has been found that the hardening effects of microstructure and crystallography are only significant at very low-oxygen concentrations, whereas interstitial solid solution hardening dominates by order of magnitude for higher oxygen concentrations. The role of microstructure on oxygen ingress has been studied and oxygen ingress along a potential α/β interface was directly observed on the nanoscale using APT.

Laboratory study of low-sulfide tailings covers with elevated water table to prevent acid mine drainage

The use of monolayer covers combined with an elevated water table (EWT) is a promising reclamation method that relies on the low gas-diffusivity of water to limit oxygen ingress into potentially acid-generating tailings. A monolayer cover is installed over the sulfidic material and the water table level is controlled to maintain the tailings close to saturation. A protocol including laboratory columns was conducted to evaluate the sensitivity of the technique to parameters including cover thickness, water table level, and the presence of an anti-evaporation layer. Two types of desulfurized tailings were evaluated: silty tailings from Westwood mine and sandy tailings from Goldex mine. Data used to evaluate the covers performances included volumetric water content, suction, oxygen concentrations, and oxygen consumption. Results showed that both cover materials could be used to maintain the reactive tailings at a degree of saturation ≥90% when the EWT level was maintained at a maximum distance of 1 m below the tailings surface. The finer Westwood material showed a better capacity for limiting oxygen migration through the cover, with a maximum flux of 5.7 mol·m−2·year−1 measured near the cover base.

CANNING FOOD IN SEMI-RIGID POLYMERIC AND COMPOSITE CONTAINERS

For thermal preservation of food, various types of retail polymeric packaging can be used: rigid, semi-rigid, flexible, and other kinds of containers. To make polymeric (plastic) containers usable for thermal sterilisation, and to ensure long storage of food, they should have a barrier layer that will make them heat-resistant, prevent oxygen ingress, and preserve the product’s quality and nutritive value. Every polymer material has its individual heat resistance characteristics. This paper considers such retail containers for food packaging as a composite can made of metal with a plastic lid and a semi-rigid heat-resistant polymer container with a foil cover. When using different container types for heat sterilisation and prevention of physical defects in cans, the following technological characteristics of cans should be taken into account: closure strength, depressurisation pressure, method of closure, diameter of a container’s opening, absence or presence of a stiffness relief on the cover, temperature of packaging, and other factors. The research includes analysis of existing types of retail composite and polymeric containers for canning food using different heat sterilisation methods. The theoretical and experimental research conducted has resulted in obtaining the values of the closure strength of the containers, an important parameter without which proper heat sterilisation of a product would be impossible. Developing scientifically proved parameters and modes of high-temperature sterilisation of meat and fish products in semi-rigid heat-resistant composite metal-plastic containers will allow enterprises to manufacture high-quality and safe canned food with high nutritive value.

Suppressing the oxygen ingress into Ti-alloys by a one-step Al- plus F-treatment

Oxygen ingress into technical Ti-alloys during high temperature exposure in oxygen containing environments leads to an enriched surface zone due to the high oxygen solubility in titanium. This affected zone is known as alpha case and is embrittled compared to the substrate material. Therefore, the operating temperature of these alloys is limited. An enrichment of Al in the surface zone of Ti-alloys leads to an improvement by the formation of intermetallic TixAly-phases with decreased oxygen solubility. This one-step Al-enrichment plus a F-treatment is proposed for the formation of a continuous stable alumina scale which prevents oxygen inward diffusion. In this paper the results of high temperature exposure tests in air of technical Ti-alloys are presented without any treatment and treated with Al-enrichment including fluorination. Post experimental investigations such as SEM reveal the formation of thin alumina layers on treated samples. Hardness measurements confirm that no embrittlement was observed for the treated samples while untreated specimens show increased hardness values in the subsurface zone corresponding with the oxygen inward diffusion profile.

Amorphous Alumina Films Efficiently Protect Ti6242S against Oxidation and Allow Operation above 600 °C

The protection of the titanium based Ti6242S alloy against oxidation at moderate temperature is investigated, through the application on its surface of a 300 nm thick, amorphous alumina film. The latter is processed by metalorganic chemical vapor deposition at 500 °C from dimethyl aluminum isopropoxide. Upon oxidation at 600 °C for 5000 h, an interfacial zone is created between the alloy and the external protective layer, composed of unaffected alumina. In these conditions, the mass gain per unit area is eight times lower than that of the bare alloy, while the hardness of the alloy remains unaffected, revealing negligible oxygen ingress attributed to the efficiency of the protective coating. Finally, alumina coated samples show negligible mass change after 80 one-hour thermal cycles between 50 °C and 600 °C, showing excellent coating adherence on the Ti alloy.

Oxygen desorption and oxygen transfer through oak staves and oak stave gaps: an innovative permeameter

During wine aging, several complex phenomena take place in barrels according to oak’s intrinsic physical properties. This research aims to better understand oxygen desorption and oxygen transfer phenomena through oak staves and especially through stave gaps in order to reevaluate the importance of barrel-making in barrel’s oxygen supply. Experimentation was based on the development of an innovative permeameter. With this permeameter, we could estimate gas transfer through oak staves and between oak stave gaps. With a specially developed tightening system, the existing pressure at stave gaps in a barrel could be reproduced on a laboratory scale in order to estimate its influence on oxygen transfer efficiency. Results proved that oxygen transfer through intact oak wood is limited; the main oxygen transfer takes place (i) through weak zones caused by fragile contact between staves and (ii) with low pressure between two staves (mainly in the middle of the side pieces). So, it is identified that oxygen transfer through stave gaps is largely impacted by applied pressure and by contact conditions on the surfaces of adjacent staves. This research also proves that oxygen desorption plays an important part in total oxygen ingress. These results confirm that the barrel-making process has a strong impact on a barrel’s oxygen supply during the aging process.